Method of producing analytical tool

ABSTRACT

The invention relates to a method of producing an analytical tool having recesses ( 20 ) formed therein for moving a sample liquid, a base plate ( 2 ) made of polymeric material, and a cover laminated to the base plate ( 2 ) to cover the recesses ( 20 ). This producing method includes the step of applying a hydrophilic treatment to the inner surfaces of the recesses ( 20 ). The hydrophilic treatment includes a primary modifying operation for primarily modifying the properties of the inner surfaces of the recesses ( 20 ) by contacting a modifying gas with the inner surfaces of the recesses ( 20 ), and a secondary modifying operation for secondarily modifying the properties of the inner surfaces of the recesses ( 20 ).

TECHNICAL FIELD

The present invention relates to a method of producing an analyticaltool which is used for analyzing a sample liquid and which is structuredto move the sample liquid before the analysis.

BACKGROUND ART

In one type of analytical tool, a sample liquid is caused to move bycapillary action. Such an analytical tool includes a capillary forproducing a capillary force. To properly exert the capillary force ontoa sample liquid, the inner surface of the capillary is hydrophilicallytreated. For example, in the structure shown in FIG. 9, a capillary 93is formed by covering a groove 91 formed in a substrate 90 with a cover92. In this case, the bottom surface 91 a of the groove 91 and onesurface 92 a of the cover 92 are hydrophilically treated. Thehydrophilization treatment with respect to the inner surface of thecapillary 93 may be performed by ultraviolet irradiation, theapplication of a surface-active agent or plasma discharge such as glowdischarge or corona discharge, for example. (See JP-A 2001-159618 andJP-A 2002-168821, for example.)

Recently, there is a tendency to reduce the sectional area of thecapillary 93 to respond to the demand for the reduction of the amount ofa sample liquid and the size reduction of an analytical tool.Particularly, in an analytical tool including a plurality of capillariesfor analyzing a plurality of items, it is highly necessary to reduce thesectional area of each capillary. Since a typical analytical tooloriginally has a relatively small thickness, to effectively reduce thesize of the analytical tool, the dimension of the tool as viewed in planneed be reduced. As shown in FIG. 10, to reduce the sectional area ofeach of capillaries 93 while reducing the size of the analytical tool aswell, the width of each capillary 93 need be reduced. However, when thewidth of the capillary 93 is reduced to reduce the sectional area, theproportion of the hydrophilically-treated surfaces decreases in the casewhere hydrophilization treatment is performed only with respect to thebottom surface 91 a of each groove 91 and to one surface 92 a of thecover 92. Therefore, to properly move the sample liquid through thecapillary 93, the hydrophilization treatment need be performed also withrespect to the side surfaces 91 b of the groove 91.

However, it is difficult to hydrophilically treat the side surfaces 91 bof the groove 91 by the application of a surface-active agent orultraviolet irradiation. Specifically, since light such as ultravioletrays has linearity, it is difficult to cause ultraviolet rays to impingeon the side surface 91 b of such a small flow path (groove) 91 as shownin FIG. 11A.

The hydrophilization treatment by the application of a surface-activeagent is performed by supplying a liquid material containing asurface-active agent into the groove 91 and then drying the liquidmaterial. Therefore, to apply the surface-active agent to the sidesurfaces 91 b of the groove 91, it is necessary to completely fill thegroove 91 with the liquid material and then dry the liquid material, asshown in FIG. 11B. In this way, since the groove 91 is filled with thesurface-active agent to apply the surface-active agent to the sidesurface of the groove 91, the provision of a flow path having anintended sectional area is difficult.

The hydrophilization treatment by utilizing plasma discharge requiresequipment for causing plasma discharge and hence requires high cost ofequipment and manufacturing cost. Further, similarly to thehydrophilization treatment by ultraviolet irradiation, it is difficultto hydrophilically treat the side surfaces 91 b of the groove 91satisfactorily by plasma discharge.

DISCLOSURE OF THE INVENTION

An object of the present invention is to provide a method which iscapable of properly performing hydrophilization even with respect to asmall flow path without increasing the cost.

According to the present invention, there is provided a method ofproducing an analytical tool which comprises a substrate made of apolymer material and formed with a groove for moving a sample liquid,and a cover bonded to the substrate to cover the groove. The methodcomprises hydrophilically treating an inner surface of the groove. Thehydrophilization treatment includes a primary modifying step forprimarily modifying characteristics of the inner surface of the grooveby bringing a modifying gas into contact with the inner surface of thegroove, and a secondary modifying step for secondarily modifying thecharacteristics of the inner surface of the groove.

In the hydrophilization treatment, by the primary modifying step and thesecondary modifying step, a carboxyl group, which is a hydrophilicgroup, is introduced into a polymer chain existing at a surface of thesubstrate, for example. Thus, the inner surface of the groove becomeshydrophilic. The degree of hydrophilization is such that the contactangle of pure water at the inner surface of the groove becomes 0˜80degrees, and preferably 0˜60 degrees, for example.

The hydrophilization treatment may be performed before the cover isbonded to the substrate or after the cover is bonded to the substrate.In the latter case, when the cover is made of a polymer material, notonly the inner surface of the groove but also the surface of the coverwhich faces the groove can be hydrophilically treated.

The primary modifying step may be performed for 1˜60 minutes under suchconditions that the partial pressure of the modifying gas is maintainedat 10˜2000 hPa and temperature is maintained at 0˜100° C., andpreferably, the partial pressure of the modifying gas is maintained at100˜1100 hPa and temperature is maintained at 0˜40° C. Preferably, inthe primary modifying step, use is made of a modifying gas containingfluorine gas and oxygen gas. Preferably, in this case, the mixing ratioof the fluorine gas and the oxygen gas is 1:1˜1000 on a volume basis.

For example, the secondary modifying step comprises bringing water orwater vapor into contact with the inner surface of the groove. Thebringing of water or water vapor into contact with the inner surface ofthe groove may comprise spraying water or water vapor to an innersurface of the substrate or immersing the substrate in a water bath. Thesubstrate may be brought into contact with air for secondarily modifyingthe inner surface of the groove by the moisture contained in the air. Inthis case, use may be made of air which has been positively caused tocontain moisture.

The present invention is applicable to an analytical tool in which asample liquid is caused to move by capillary action as a technique formaking the inner surface of the fluid path hydrophilic. Particularly,the present invention is applicable to such an analytical tool as amicrodevice which includes a small fluid path. For example, the presentinvention is applicable to a microdevice which includes a fluid pathhaving a principal cross section (corresponding to the principal crosssection of the groove of the substrate) having a rectangular shape whichhas a width W of 10˜500 μm and a depth D of 5˜500 μm and satisfiesD/W≧0.5. The “principal cross section” herein indicates a verticalsection extending perpendicularly to the travel direction of the sampleliquid, and indicates the vertical section of a portion which is mainlyutilized for traveling the sample liquid when the sectionalconfiguration is not uniform.

In the present invention, the primary modifying step is performed byusing modifying gas (gas), whereas the secondary modifying step isperformed by using gas or liquid such as water vapor or water, forexample. Since these substances do not have such linearity as that ofultraviolet rays, the substances such as modifying gas and water vaporcan be reliably brought into contact with the inner surface of thegroove of the substrate. Therefore, the entirety of the inner surface ofthe groove can be hydrophilically treated reliably. Such an advantagecan be obtained also in producing a microdevice including a small flowpath (a groove having a small sectional area). Moreover, since theapparatus for supplying modifying gas, water or water vapor can have asimple structure and can be manufactured at a low cost, the method isadvantageous in terms of the manufacturing cost.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 an entire perspective view showing an example of microdevice asan object to be produced by the method of the present invention.

FIG. 2 is a sectional view taken along lines II-II in FIG. 1, part ofwhich is shown as enlarged.

FIG. 3 is an entire perspective view showing the cover of themicrodevice.

FIG. 4 is an entire perspective view showing the substrate of themicrodevice.

FIG. 5 is a sectional view showing a primary modifying step of thehydrophilization step in the production method of the present invention.

FIG. 6 is a sectional view showing a secondary modifying step of thehydrophilization step in the production method of the present invention.

FIG. 7 is a sectional view showing another example of secondarymodifying step of the hydrophilization step in the production method ofthe present invention.

FIG. 8 is a sectional view showing a bonding step in the productionmethod of the present invention.

FIG. 9 is a sectional view of an analytical tool for describing a priorart method.

FIG. 10 is a sectional view of an analytical tool for describing a priorart method.

FIGS. 11A and 11B are sectional views for describing prior arthydrophilization treatment.

BEST MODE FOR CARRYING OUT THE INVENTION

The present invention relates to a method of producing an analyticaltool which is mounted, in use, to an analytical apparatus. In theanalytical apparatus, a sample liquid supplied to the analytical tool isanalyzed by an optical method or an electrochemical method, for example.

FIGS. 1-4 show an example of analytical tool to be produced by a methodaccording to the present invention. The analytical tool 1 shown in thefigures is a so-called microdevice and designed to perform analysis of asample by an optical method. The microdevice 1, which serves to providea reaction field, includes a substrate 2 formed with a groove 20, and acover 3 bonded to the substrate 2 via an adhesive sheet 4 to cover thegroove 20.

As better shown in FIGS. 1 and 4, the groove 20 includes a sampleintroduction path 21, a reagent introduction path 22 and a reaction path23. The reaction path 23 has an end 23 a connected to the sampleintroduction path 21 and the reagent introduction path 22. The entiretyof the reaction path 23 has a serpentine shape to have a long length.The reaction path 23 has another end 23 b which provides a measurementportion to be irradiated with light from a measurement light source.

As shown in FIG. 2, the groove 20 has a principal rectangular crosssection which has a width W of 10˜500 μm and a depth D of 5˜500 μm andwhich satisfies D/W≧0.5. The inner surface of the groove 20 ishydrophilically treated. The contact angle of pure water at the innersurface of the groove 20 is 0˜80 degrees, for example.

As shown in FIGS. 1 through 3, the cover 3 includes a sampleintroduction port 30, a reagent introduction port 31 and an air vent 32.The sample introduction port 30 is provided at a location correspondingto an end 21 a of the sample introduction path 21, the reagentintroduction port 31 provided at a location corresponding to an end 22 aof the reagent introduction path 22, and the air vent 32 provided at alocation corresponding to the end 23 b of the reaction path 23.

For analyzing a sample, the sample and a reagent are introduced to themicrodevice 1 through the sample introduction port 30 and the reagentintroduction port 31, respectively. The sample and the reagent move, bycapillary action, through the sample introduction path 21 and thereagent introduction path 22, respectively, to merge at the reactionpath 23. As a result, reaction between the sample and the reagentstarts. The sample and the reagent, while undergoing the reaction,travel through the reaction path 23 toward the air vent 23 by capillaryaction and finally reach the measurement portion 23 b. At themeasurement portion 23 b, the reaction product of the sample and thereagent is analyzed by the analytical apparatus, as noted above.

A method of producing the microdevice 1 will be described below.Hereinafter, a method for producing a microdevice individually one byone will be exemplarily described.

The method of producing a microdevice 1 includes a cover forming step, asubstrate forming step, a hydrophilization step and a bonding step.

In the cover forming step, a transparent resin film, for example, issubjected to punching and then cut into an intended size (See FIG. 3).By the punching, through-holes are formed, which are later to become thesample introduction port 30, the reagent introduction port 31 and theair vent 32. In the step for forming the cover 3, punching of the resinfilm may be performed after cutting of the resin film. One surface ofthe cover 3 may be hydrophilically treated by ultraviolet irradiation orthe application of a surface-active agent. Examples of material of theresin film (material of the cover 3) include polymer materials such aspolydimethylsiloxane (PDMS), polymethyl methacrylate (PMMA), polystyrene(PS), polycarbonate (PC) and polyethylene terephthalate (PET). The resinfilm (cover 3) may be made of a combination of at least two polymermaterials. For example, the resin film (cover 3) may be made of amaterial provided by blending at least two of the polymer materialsexemplified above. Alternatively, the resin film (cover 3) may be formedby bonding films or sheets which are made of different polymer materialstogether.

In the substrate forming step, a substrate is formed by injectionmolding using a thermoplastic resin, for example. In the injectionmolding, the groove 20 can be formed in the substrate 2 by appropriatelydesigning the configuration of the mold. Alternatively, the groove 20may be made by laser beam machining or etching, for example. Examples ofmaterial of the substrate include polymer materials such as polymethylmethacrylate (PMMA), polystyrene (PS), polycarbonate (PC) andpolyethylene terephthalate (PET).

The hydrophilization step includes a primary modifying step forprimarily modifying the characteristics of the inner surface of thegroove 20 by bringing a modifying gas into contact with the innersurface of the groove 20, and a secondary modifying step for secondarilymodifying the characteristics of the inner surface of the groove 20.

As shown in FIG. 5, for example, the primary modifying step is performedwith a plurality of substrates 2 housed in a chamber 5. To the chamber 5are connected a modifying gas supply pipe 50 for supplying the modifyinggas to the chamber 5, and a purge pipe 51 for discharging gas from thechamber 5.

As the modifying gas, use may be made of gas containing fluorine gas andoxygen gas, for example. In this case, the mixing ratio of fluorine gasand oxygen gas is 1:1˜1000, and preferably, 1:10˜20 on a volume basis.During the primary modifying step, the interior of the chamber 5 is somaintained that the partial pressure of the modifying gas is 10˜2000 hPaand the temperature is 0˜100° C., and preferably, the partial pressureof the modifying gas is 100˜1100 hPa and the temperature is 0˜40° C.Under such conditions, the substrate 2 is kept in contact with themodifying gas for 1 to 60 minutes, for example. As a result, in apolymer chain forming the substrate 2, a fluorine atom is introduced toa side chain or an end group as bonded to a keto ketene group.

The secondary modifying step is performed by bringing water or watervapor into contact with the inner surface of the groove 20. As a result,the fluorine atom previously introduced is replaced with a hydroxylgroup, whereby a carboxyl group is introduced into the polymer chain.Thus, the inner surface of the groove 20 becomes hydrophilic.

For example, the contact of the inner surface of the groove 20 withwater or water vapor may be performed by supplying water or water vaporto the chamber 6 accommodating the substrates 2, as shown in FIG. 6. Thesubstrates 2 may be brought into contact with water or water vapor in anopen system. The inner surface of the groove 20 may be brought intocontact with water by immersing the substrates 2 in water 70 stored in acontainer 7, as shown in FIG. 7. The secondary modifying step may beperformed by replacing the mixed gas contained in the chamber 6 with airto bring moisture contained in the air into contact with the innersurface of the groove 20. In this case, use may be made of air which hasbeen positively caused to contain moisture or indoor air.

For example, the bonding step is performed by interposing an adhesivesheet 4 between the substrate 2 and the cover 3, and then applying apressing force to the adhesive sheet 4, as shown in FIG. 8. As theadhesive sheet 4, use may be made of whose opposite surfaces areadherent and which is formed with openings 40 and 42 at locationscorresponding to the sample introduction port 30, the reagentintroduction port 31 and the air vent 32 of the substrate 2.

In the hydrophilization step of this embodiment, the primary modifyingstep is performed by using a modifying gas (gas), whereas the secondarymodifying step is performed by using gas or liquid such as water vaporor water. Since these substances do not have such linearity as that ofultraviolet rays, the substances such as a modifying gas and water vaporcan be reliably brought into contact with the inner surface of thegroove 20. Therefore, the entirety of the inner surface of the groove 20can be hydrophilically treated reliably. Such an advantage can beobtained also in producing a microdevice 1 including a small flow path(a groove 20 having a small sectional area). Moreover, since theapparatus for supplying a modifying gas, water or water vapor can have asimple structure and can be manufactured at a low cost, the method isadvantageous also in terms of the manufacturing cost.

The present invention is not limited to the foregoing embodiments butmay modified in various ways. For example, although the hydrophilizationwith respect to the substrate is performed before the cover is bonded tothe substrate in the foregoing embodiments, the hydrophilization may beperformed after the cover is bonded to the substrate. In such a case,not only the inner surface of the groove but also the surface of thecover which faces the flow path can be hydrophilically treated.

The present invention is also applicable to such microdevices as onethat mixes three or more liquids, one that is formed with a plurality offluid paths for providing a plurality of reaction systems, and one whichcontains a reagent in the fluid path so that only a sample liquid isintroduced to the fluid path. The present invention is also applicableto microdevices for analyzing a sample by an electrochemical method aswell as those for analyzing a sample by an optical method.

The present invention is also applicable to the case where a pluralityof analytical tools are to be produced at the same time. For example, aplate member including a plurality of portions which are later to becomesubstrates may be formed by resin-molding, and then the plate member maybe hydrophilically treated. In this case, another plate member includinga plurality of portions which are to become covers is bonded to theplate member, and then the bonded product is cut, whereby a plurality ofanalytical tools are provided at the same time.

In the foregoing embodiments, an adhesive sheet and a cover in whichthrough-holes are formed in advance are bonded to the substrate.However, through-holes may be formed in the adhesive sheet and the coverafter the adhesive sheet and the cover are bonded to the substrate.

The bonding of the cover to the substrate may not necessarily beperformed by using the adhesive sheet. For example, the bonding may beperformed by using an adhesive or by heat seal or ultrasonic fusing.

According to the present invention, hydrophilization can be properlyperformed not only with respect to a groove having a rectangular crosssection but also to a groove having another cross sectionalconfiguration such as a semi-circular cross section or a triangularcross section.

1. A method of producing an analytical tool comprising a substrate madeof polymethyl methacrylate having a keto group and formed with a groovefor moving a sample liquid, and a cover bonded to the substrate to coverthe groove, the method comprising: hydrophilically treating an innersurface of the groove of the substrate; and bonding the cover to thehydrophilized substrate; wherein the hydrophilization for the substrateincludes a primary modifying step for bringing a modifying gas intocontact with the inner surface of the groove to cause a primarysubstitution group from the modifying gas to bond to the keto group ofthe polymethyl methacrylate, and a secondary modifying step forsubstituting the primary substitution group bonded to the keto groupwith a hydroxyl group.
 2. The analytical tool producing method accordingto claim 1, wherein the modifying gas contains fluorine gas and oxygengas.
 3. The analytical tool producing method according to claim 2,wherein mixing ratio of the fluorine gas and the oxygen gas is 1:1˜1000on a volume basis.
 4. The analytical tool producing method according toclaim 3, wherein mixing ratio of the fluorine gas and the oxygen gas is1:10˜20 on a volume basis.
 5. The analytical tool producing methodaccording to claim 1, wherein the primary modifying step is performedfor 1˜60 minutes under conditions where partial pressure of themodifying gas is maintained at 10˜2000 hPa and temperature is maintainedat 0˜100° C.
 6. The analytical tool producing method according to claim5, wherein the partial pressure of the modifying gas is maintained at100˜1100 hPa and the temperature is maintained at 0˜40° C.
 7. Theanalytical tool producing method according to claim 1, wherein thesecondary modifying step comprises bringing water or water vapor intocontact with the inner surface of the groove.
 8. The analytical toolproducing method according to claim 7, wherein the bringing of water orwater vapor into contact with the inner surface of the groove comprisesspraying water or water vapor to an inner surface of the substrate. 9.The analytical tool producing method according to claim 7, wherein thebringing of water or water vapor into contact with the inner surface ofthe groove comprises immersing the substrate in a water bath.
 10. Theanalytical tool producing method according to claim 7, wherein thebringing of water or water vapor into contact with the inner surface ofthe groove comprises leaving the substrate in air.
 11. The analyticaltool producing method according to claim 10, wherein the air ispositively caused to contain moisture.
 12. The analytical tool producingmethod according to claim 1, wherein the hydrophilization treatment forthe substrate is so performed that a contact angle of pure water at theinner surface of the groove becomes 0˜80 degrees.
 13. The analyticaltool producing method according to claim 12, wherein the contact angleis 0˜60 degrees.
 14. The analytical tool producing method according toclaim 1, wherein the analytical tool is designed to move the sampleliquid by capillary action.
 15. The analytical tool producing methodaccording to claim 14, wherein the groove has a principal, rectangularcross section which has a width W of 10˜500 μm and a depth D of 5˜500 μmand which satisfies D/W≧0.5.